Optical image measurement device and image processing device

ABSTRACT

An optical image measurement device is configured to form a tomographic image at each of a plurality of cross sections of a measurement object, and the optical image measurement device comprises: an image processor configured to execute an arithmetic operation based on a tomographic image at one cross section of the plurality of cross sections and another tomographic image at each of one or more cross sections other than the one cross section, thereby forming a new tomographic image at the one cross section.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical image measurement device andimage processing device for imaging the morphology of a measurementobject of a light-scattering medium, based on the reflected light ortransmitted light of a light beam applied to the measurement object, andspecifically relates to a technique that is favorably applicable to afundus oculi observation.

2. Description of the Related Art

As a device for observing the fundus oculi of an eye (fundus oculiobservation device), a retinal camera has been widely usedconventionally. FIG. 12 shows an example of the appearance of a generalretinal camera used conventionally. FIG. 13 shows an example of theconfiguration of an optical system internally accommodated in theretinal camera (see Japanese Unexamined Patent Application PublicationJP-A 2004-350849, for example). Herein, an “observation” includes atleast an observation of a captured fundus oculi image (a fundus oculiobservation with a naked eye may be included).

First, referring to FIG. 12, the appearance of a conventional retinalcamera 1000 will be described. This retinal camera 1000 is provided witha platform 3 mounted on a base 2 so as to be slidable in the front andrear, right and left directions (horizontal directions). On thisplatform 3, an operation panel and a control lever 4 for an examiner toperform various operations are mounted.

The examiner can 3-dimensionally move the platform 3 on the base 2 byoperating the control lever 4. On the top of the control lever 4, anoperation button 4 a pressed down at the time of capturing a fundusoculi is mounted.

On the base 2, a post 5 is mounted standing upward. This post 5 isprovided with a jaw rest 6 where a jaw of a subject is rested, and anexternal fixation lamp 7 serving as a light source for fixing an eye E.

On the platform 3, a main body part 8 is placed for accommodatingvarious optical systems and control systems of the retinal camera 1000.The control system may be placed, for example, inside the base 2 or theplatform 3, or in an external device such as a computer connected to theretinal camera 1000.

On the eye E side of the main body part 8 (i.e., on the left side on thesheet of FIG. 12), an objective lens part 8 a placed facing the eye E isdisposed. Moreover, on the examiner's side (i.e., on the right side onthe sheet of FIG. 12), an eyepiece part 8 b for observing the fundusoculi of the eye E with naked eyes is disposed.

Furthermore, to the main body part 8, a still camera 9 for producing astill image of the fundus oculi of the eye E and an imaging device 10such as a TV camera for producing a still image or moving image of thefundus oculi are disposed. The still camera 9 and the imaging device 10are formed so as to be removable from the main body part 8.

As the still camera 9, in accordance with various conditions such as thepurpose of an examination and a method of saving a captured image, adigital camera equipped with an imaging device such as a CCD (chargecoupled device) and a CMOS (complementary metal oxide semiconductor), afilm camera, an instant camera and the like may be interchangeably usedas necessary. The main body part 8 is provided with a mounting part 8 cfor interchangeably mounting the still camera 9.

In a case where the still camera 9 and the imaging device 10 are ofdigital imaging type, it is possible to send image data of fundus oculiimages captured by these components to a computer or the like connectedto the retinal camera 1000, and observe by displaying the fundus oculiimages on a display. Further, it is possible to send the image data toan image recording device connected to the retinal camera 1000 andcreate a database, and use it as, for example, electronic data forcreating an electronic medical record.

Further, on the examiner's side of the main body part 8, a touch panelmonitor 11 is disposed. On this touch panel monitor 11, a fundus oculiimage of the eye E formed based on video signals outputted from the(digital-type) still camera 9 or imaging device 10 is displayed.Moreover, on the touch panel monitor 11, an x-y coordinate system takingthe center of a screen as the origin is displayed superimposed on thefundus oculi image. When the examiner touches the screen, coordinatevalues corresponding to a touched position are displayed.

Next, referring to FIG. 13, the configuration of the optical system ofthe retinal camera 1000 will be described. The retinal camera 1000 isprovided with an illumination optical system 100 that illuminates afundus oculi Ef of the eye E, and an imaging optical system 120 thatguides the illumination light reflected by the fundus oculi to theeyepiece part 8 b, the still camera 9 and the imaging device 10.

The illumination optical system 100 comprises: an observation lightsource 101; a condenser lens 102; an imaging light source 103; acondenser lens 104; exciter filters 105 and 106; a ring transparentplate 107; a mirror 108; an LCD 109; an illumination diaphragm 110; arelay lens 111; an aperture mirror 112; and an objective lens 113.

The observation light source 101 is composed of, for example, a halogenlamp, and emits continuous light for fundus oculi observation. Thecondenser lens 102 is an optical element for converging the continuouslight (observation illumination light) emitted by the observation lightsource 101 and almost evenly applying the observation illumination lightto the fundus oculi Ef.

The imaging light source 103 is composed of, for example, a xenon lamp,and is flashed at the time of imaging of the fundus oculi Ef. Thecondenser lens 104 is an optical element for converging the flash light(imaging illumination light) emitted by the imaging light source 103 andevenly applying the imaging illumination light to the fundus oculi Ef.

The exciter filters 105 and 106 are filters used at the time offluorography of an image of the fundus oculi Ef. The exciter filters 105and 106 can be respectively inserted into and removed from an opticalpath by a drive mechanism (not illustrated) such as a solenoid. Theexciter filter 105 is placed on the optical path at the time of FAG(fluorescein angiography). The exciter filter 106 is placed on theoptical path at the time of ICG (indocyanine green angiography). At thetime of color-imaging, both the exciter filters 105 and 106 areretracted from the optical path.

The ring transparent plate 107 is placed in a conjugating position witha pupil of the eye E, and is provided with a ring transparent part 107 ataking the optical axis of the illumination optical system 100 as thecenter. The mirror 108 reflects the illumination light emitted by theobservation light source 101 or imaging light source 103, in a directionof the optical axis of the imaging optical system 120. The LCD 109displays a fixation target (not illustrated) for fixing the eye E.

The illumination diaphragm 110 is a diaphragm member to shut out part ofthe illumination light in order to prevent flare and the like. Thisillumination diaphragm 110 is configured so as to be movable in theoptical axis direction of the illumination optical system 100, and isthus capable of changing an illumination region of the fundus oculi Ef.

The aperture mirror 112 is an optical element that combines the opticalaxis of the illumination optical system 100 and the optical axis of theimaging optical system 120. In the center region of the aperture mirror112, an aperture 112 a is opened. The optical axis of the illuminationoptical system 100 and the optical axis of the imaging optical system120 cross each other at a substantially central position of the aperture112 a. The objective lens 113 is installed in the objective lens part 8a of the main body part 8.

The illumination optical system 100 having such a configurationilluminates the fundus oculi Ef in the following manner. First, at thetime of fundus oculi observation, the observation light source 101 isturned on and an observation illumination light is emitted. Thisobservation illumination light is applied to the ring transparent plate107 through the condenser lenses 102 and 104 (the exciter filters 105and 106 are retracted from the optical path). The light passed throughthe ring transparent part 107 a of the ring transparent plate 107 isreflected by the mirror 108 and, after passing through the LCD 109, theillumination diaphragm 110 and the relay lens 111, is reflected by theaperture mirror 112. The observation illumination light reflected by theaperture mirror 112 travels in the optical axis direction of the imagingoptical system 120, and is converged by the objective lens 113, therebyentering the eye E and illuminate the fundus oculi Ef.

At this moment, since the ring transparent plate 107 is placed in aconjugating position with the pupil of the eye E, a ring-shaped image ofthe observation illumination light entering the eye E is formed on thepupil. The entering fundus oculi reflection light of the enteredobservation illumination light is emitted from the eye E through acentral dark part of the ring-shaped image on the pupil. Thus, theobservation illumination light entering the eye E is prevented fromaffecting the fundus oculi reflection light of the observationillumination light.

On the other hand, at the time of imaging of the fundus oculi Ef, flushlight is emitted from the imaging light source 103, and the imagingillumination light is applied to the fundus oculi Ef through the samepath. In the case of fluorography, either the exciter filter 105 or theexciter filter 106 is selectively placed on the optical path, dependingon whether FAG imaging or ICG imaging is carried out.

Next, the imaging optical system 120 will be described. The imagingoptical system 120 comprises: an objective lens 113; an aperture mirror112 (an aperture 112 a thereof); an imaging diaphragm 121; barrierfilters 122 and 123; a variable magnifying lens 124; a relay lens 125;an imaging lens 126; a quick return mirror 127; and an imaging media 9a. Herein, the imaging media 9 a is an imaging media (a CCD, camerafilm, instant film or the like) for the still camera 9.

The fundus oculi reflection light of the illumination light exiting fromthe eye E through the central dark part of the ring-shaped image formedon the pupil enters the imaging diaphragm 121 through the aperture 112 aof the aperture mirror 112. The aperture mirror 112 reflects corneareflection light of the illumination light, and acts so as not to mixthe cornea reflection light into the fundus oculi reflection lightentering the imaging diaphragm 121. Consequently, generation of flare inobservation images and captured images is inhibited.

The imaging diaphragm 121 is a plate-shaped member having a plurality ofcircular light-transmitting parts of different sizes. The plurality oflight-transmitting parts compose diaphragms with different diaphragmvalues (F values), and are placed alternatively on the optical path by adrive mechanism (not illustrated).

The barrier filters 122 and 123 can be inserted into and removed fromthe optical path by a drive mechanism (not illustrated) such as asolenoid. In FAG imaging, the barrier filter 122 is placed on theoptical path, whereas in ICG imaging, the barrier filter 123 is placedon the optical path. Further, at the time of color-imaging, both thebarrier filters 122 and 123 are retracted from the optical path.

The variable magnifying lens 124 is movable in the optical axisdirection of the imaging optical system 120 by a drive mechanism (notillustrated). This makes it possible to change an observation magnifyingratio and an imaging magnifying ratio, and to focus images of the fundusoculi. The imaging lens 126 is a lens that focuses the fundus oculireflection light from the eye E onto the imaging media 9 a.

The quick return mirror 127 is disposed so as to be capable of beingrotated around a rotary shaft 127 a by a drive mechanism (notillustrated). In a case where imaging of the fundus oculi Ef isperformed with the still camera 9, the fundus oculi reflection light isguided to the imaging media 9 a by springing up the quick return mirror127 that is obliquely mounted on the optical path. Meanwhile, in a casewhere imaging of the fundus oculi is performed with the imaging device10, or in a case where observation of the fundus oculi is performed withthe naked eye of the examiner, the quick return mirror 127 is obliquelymounted on the optical path to upwardly reflect the fundus oculireflection light.

The imaging optical system 120 is further provided with, for guiding thefundus oculi reflection light reflected by the quick return mirror 127,a field lens 128, a switching mirror 129, an eyepiece 130, a relay lens131, a reflection mirror 132, an imaging lens 133, and an image pick-upelement 10 a. The image pick-up element 10 a is an image pick-up elementsuch as a CCD installed in the imaging device 10. On the touch panelmonitor 11, a fundus oculi image Ef′ imaged by the image pick-up element10 a is displayed.

The switching mirror 129 is rotatable around a rotary shaft 129 a in thesame manner as the quick return mirror 127. This switching mirror 129 isobliquely disposed on the optical path during observation with the nakedeye, thereby reflecting and guiding the fundus oculi reflection light tothe eyepiece 130.

Further, at the time of capture of a fundus oculi image by using theimaging device 10, the switching mirror 129 is retracted from theoptical path, and the fundus oculi reflection light is guided toward theimage pick-up element 10 a. In this case, the fundus oculi reflectionlight is passed through the relay lens 131 and reflected by the mirror132, whereby an image is formed in the image pick-up element 10 a by theimaging lens 133.

This retinal camera 1000 is a fundus oculi observation device used forobserving the state of the surface of the fundus oculi Ef, namely, thestate of the retina. In other words, the retinal camera 1000 is a devicefor acquiring a 2-dimensional fundus oculi image when the fundus oculiEf is seen from the cornea of the eye E. On the other hand, organs suchas the choroidea and the sclera exist in the deeper layers of theretina. There has been a demand for a technique for observing the stateof these organs, and in recent years, there has been progress in thepractical utilization of devices for observing these deeper layer organs(refer to Japanese Unexamined Patent Application Publications Nos. JP-A2003-000543 and JP-A 2005-241464).

Each of the devices disclosed in JP-A 2003-000543 and JP-A 2005-241464is an optical image measurement device to which a so-called OCT (OpticalCoherence Tomography) technology is applied (referred to as an opticalcoherence topography device, or the like). Such an optical imagemeasurement device is a device that splits low-coherence light into two,guides one (signal light) of the lights to the fundus oculi and theother (reference light) to a given reference object, and detects andanalyzes interference light obtained by superimposing the signal lightpassed through the fundus oculi and the reference light reflected by thereference object, thereby forming tomographic images of the surface anddeep layer tissue of the fundus oculi or 3-dimensional images of thefundus oculi.

However, such a conventional optical image measurement device isconfigured so as to form a tomographic image based on light (signallight) having passed through a single cross-sectional position of ameasurement object, so that a tomographic image with insufficient imagequality may be formed. Specifically, in a case where the image qualityof an image subjected to diagnosis of living organs such as a fundusoculi is insufficient, there is the possible risk of situations in whichthe form of the living organs cannot be captured in detail or smalllesions are overlooked.

The present invention is for solving such problems, and an object of thepresent invention is to provide an optical image measurement device andan image processing device that are capable of enhancing the imagequality of an image to be formed.

In order to achieve the aforementioned object, in a first aspect of thepresent invention, an optical image measurement device is configured toform a tomographic image at each of a plurality of cross sections of ameasurement object, and the optical image measurement device comprises:an image processor configured to execute an arithmetic operation basedon a tomographic image at one cross section of the plurality of crosssections and another tomographic image at each of one or more crosssections other than the one cross section, thereby forming a newtomographic image at the one cross section.

In a second aspect of the present invention, an image processing devicecomprises: a storage configured to store a tomographic image at each ofa plurality of cross sections of a measurement object; and an imageprocessor configured to execute an arithmetic operation based on atomographic image at one cross section of the plurality of crosssections and another tomographic image at each of one or more crosssections other than the one cross section, thereby forming a newtomographic image at the one cross section.

According to the present invention, the device is configured to executean arithmetic operation based on a tomographic image along onecross-section among a plurality of cross-sections and other tomographicimages along one or more cross-sections other than the onecross-section, thereby forming a new tomographic image along the onecross-section. Therefore, it is possible to enhance the image quality ofan image to be formed, as compared with in a conventional configurationin which an image is formed only from the result of measurement along asingle cross-section.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing an example of the entireconfiguration in a preferred embodiment of a fundus oculi observationdevice comprising an optical image measurement device according to thepresent invention.

FIG. 2 is a schematic diagram showing an example of the configuration ofa scanning unit installed in a retinal camera unit in the preferredembodiment of the fundus oculi observation device comprising the opticalimage measurement device according to the present invention.

FIG. 3 is a schematic diagram showing an example of the configuration ofan OCT unit in the preferred embodiment of the fundus oculi observationdevice comprising the optical image measurement device according to thepresent invention.

FIG. 4 is a schematic block diagram showing an example of the hardwareconfiguration of an arithmetic and control unit in the preferredembodiment of the fundus oculi observation device comprising the opticalimage measurement device according to the present invention.

FIG. 5 is a schematic block diagram showing an example of theconfiguration of a control system in the preferred embodiment of thefundus oculi observation device comprising the optical image measurementdevice according to the present invention.

FIGS. 6A and 6B are schematic diagrams showing an example of a scanningmode of signal light in the preferred embodiment of the fundus oculiobservation device comprising the optical image measurement deviceaccording to the present invention. FIG. 6A shows an example of thescanning mode of the signal light when a fundus oculi is seen from theincident side of the signal light with respect to an eye. FIG. 6B showsan example of a mode of arrangement of scanning points on each scanningline.

FIG. 7 is a schematic diagram showing an example of a scanning mode ofsignal light and a mode of a tomographic image formed along eachscanning line in the preferred embodiment of the fundus oculiobservation device comprising the optical image measurement deviceaccording to the present invention.

FIG. 8 is a flowchart showing an operation example at the time executionof optical image measurement in the preferred embodiment of the fundusoculi observation device comprising the optical image measurement deviceaccording to the present invention.

FIG. 9 is a schematic explanation view for explaining the preferredembodiment of the fundus oculi observation device comprising the opticalimage measurement device according to the present invention.

FIG. 10 is a schematic explanation view for explaining a modification ofthe preferred embodiment of the fundus oculi observation devicecomprising the optical image measurement device according to the presentinvention.

FIG. 11 is a schematic explanation view for explaining a modification ofthe preferred embodiment of the fundus oculi observation devicecomprising the optical image measurement device according to the presentinvention.

FIG. 12 is a schematic side view showing an example of the appearance ofa conventional fundus oculi observation device (retinal camera).

FIG. 13 is a schematic diagram showing an example of the internalconfiguration (optical system configuration) of a conventional fundusoculi observation device (retinal camera).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

An example of a preferred embodiment of an optical image measurementdevice and an image processing device according to the present inventionwill be described in detail referring to the drawings. Herein, the samecomponents as the conventional ones will be denoted by the samereference symbols used in FIGS. 12 and 13.

First, referring to FIGS. 1 through 5, an example of the configurationin an embodiment of the optical image measurement device according tothe present invention will be described. FIG. 1 shows the entireconfiguration of a fundus oculi observation device 1 having a functionof an optical image measurement device and a function of a retinalcamera. FIG. 2 shows the configuration of a scanning unit 141 in aretinal camera unit 1A. FIG. 3 shows the configuration of an OCT unit150. FIG. 4 shows the hardware configuration of an arithmetic andcontrol unit 200. FIG. 5 shows the configuration of a control system ofthe fundus oculi observation device 1.

[Configuration of Device]

As shown in FIG. 1, the fundus oculi observation device 1 comprises: theretinal camera unit 1A that has the same function as the retinal camera;the OCT unit 150 accommodating an optical system of an optical imagemeasurement device (OCT device); and the arithmetic and control unit 200that executes various arithmetic processes, control processes, and thelike.

The OCT unit 150 composes an example of the “optical image measurementdevice” of the present invention, along with the arithmetic and controldevice 200. Further, various types of optical members (to be describedlater) through which signal lights pass through, such as the scanningunit 141 provided in the fundus oculi camera unit 1A, are also includedin the optical image measurement device.

To the OCT unit 150, one end of a connection line 152 is attached. Tothe other end of the connection line 152, a connector part 151 isattached. This connector part 151 is mounted on a mounting part 8 cshown in FIG. 12. Moreover, a conductive optical fiber runs through theinside of the connection line 152. Thus, the OCT unit 150 and theretinal camera unit 1A are optically connected via the connection line152. The detailed configuration of the OCT unit 150 will be describedlater referring to FIG. 3.

[Configuration of Retinal Camera Unit]

The retinal camera unit 1A has almost the same appearance as theconventional retinal camera 1000 shown in FIG. 12. Moreover, as in theconventional optical system shown in FIG. 13, the retinal camera unit 1Ais provided with an illumination optical system 100 that illuminates thefundus oculi Ef of the eye E, and an imaging optical system 120 thatguides the fundus oculi reflection light of the illumination light tothe imaging device 10.

Although the details will be described later, the imaging device 10 inthe imaging optical system 120 of the present embodiment detects theillumination light having a wavelength in the near-infrared region.Moreover, this imaging optical system 120 is further provided with theimaging device 12 for detecting the illumination light having awavelength in the visible region. Moreover, this imaging optical system120 guides a signal light coming from the OCT unit 150 to the fundusoculi Ef, and guides the signal light passed through the fundus oculi Efto the OCT unit 150.

Here, as in the conventional one, the illumination optical system 100comprises: an observation light source 101; a condenser lens 102; animaging light source 103; a condenser lens 104; exciter filters 105 and106; a ring transparent plate 107; a mirror 108; an LCD 109; anillumination diaphragm 110; a relay lens 111; an aperture mirror 112;and an objective lens 113.

The observation light source 101 emits an illumination light having awavelength of the visible region included in a range of, for example,about 400 nm thorough 700 nm. Moreover, the imaging light source 103emits an illumination light having a wavelength of the near-infraredregion included in a range of, for example, about 700 nm through 800 nm.The near-infrared light emitted from this imaging light source 103 isset so as to have a shorter wavelength than the light used by the OCTunit 150 (described later).

Further, the imaging optical system 120 comprises: an objective lens113; an aperture mirror 112 (an aperture 112 a thereof); an imagingdiaphragm 121; barrier filters 122 and 123; a variable magnifying lens124; a relay lens 125; an imaging lens 126; a dichroic mirror 134; afield lens 128; a half mirror 135; a relay lens 131; a dichroic mirror136; an imaging lens 133; the imaging device 10 (image pick-up element10 a); a reflection mirror 137; an imaging lens 138; the imaging device12 (image pick-up element 12 a); a lens 139; and an LCD 140.

The imaging optical system 120 according to the present embodiment isdifferent from the conventional imaging optical system 120 shown in FIG.13 in that the dichroic mirror 134, the half mirror 135, the dichroicmirror 136, the reflection mirror 137, the imaging lens 138, the lens139 and the LCD 140 are disposed.

The dichroic mirror 134 is configured to reflect the fundus oculireflection light (having a wavelength included in a range of about 400nm through 800 nm) of the illumination light from the illuminationoptical system 100, and transmit a signal light LS (having a wavelengthincluded in a range of, for example, about 800 nm through 900 nm;described later) from the OCT unit 150.

Further, the dichroic mirror 136 is configured to transmit theillumination light having a wavelength of the visible region from theillumination optical system 100 (a visible light having a wavelength ofabout 400 nm through 700 nm emitted from the observation light source101), and reflect the illumination light having a wavelength of thenear-infrared region (a near-infrared light having a wavelength of about700 nm through 800 nm emitted from the imaging light source 103).

On the LCD 140, an internal fixation target or the like is displayed.The light from this LCD 140 is reflected by the half mirror 135 afterbeing converged by the lens 139, and is reflected by the dichroic mirror136 through the field lens 128. Then, the light passes through theimaging lens 126, the relay lens 125, the variable magnifying lens 124,the aperture mirror 112 (aperture 112 a thereof), the objective lens 113and the like, and enters the eye E. Consequently, an internal fixationtarget or the like is projected in the fundus oculi Ef of the eye E.

The image pick-up element 10 a is an image pick-up element such as a CCDand a CMOS installed in the imaging device 10 such as a TV camera, andis particularly used for detecting light having a wavelength of thenear-infrared region (that is, the imaging device 10 is an infrared TVcamera for detecting near-infrared light). The imaging device 10 outputsvideo signals as a result of detection of the near-infrared light. Atouch panel monitor 11 displays a 2-dimensional image (a fundus oculiimage Ef′) of the surface of the fundus oculi Ef, based on the videosignals. The video signals are sent to the arithmetic and control unit200, and the fundus oculi image is displayed on the display (describedlater). At the time of imaging of the fundus oculi by the imaging device10, for example, the illumination light emitted from the imaging lightsource 103 of the illumination optical system 100 and having awavelength of the near-infrared region is used.

On the other hand, the image pick-up element 12 a is an image pick-upelement such as a CCD and a CMOS installed in the imaging device 12 suchas a TV camera, and is particularly used for detecting light having awavelength of the visible region (that is, the imaging device 12 is a TVcamera for detecting visible light). The imaging device 12 outputs videosignals as a result of detection of the visible light. The touch panelmonitor 11 displays a 2-dimensional image (fundus oculi image Ef′) ofthe surface of the fundus oculi Ef, based on the video signals. Thevideo signals are sent to the arithmetic and control unit 200, and thefundus oculi image Ef′ is displayed on the display (described later). Atthe time of imaging of the fundus oculi by the imaging device 12, forexample, the illumination light emitted from the observation lightsource 101 of the illumination optical system 100 and having awavelength of the visible region is used.

The imaging optical system 120 according to the present embodiment isprovided with 150 a scanning unit 141 and a lens 142. The scanning unit141 includes a component for scanning at an application position of thefundus oculi Ef with light emitted from the OCT unit (signal light LS;described later).

The lens 142 makes the signal light LS guided from the OCT unit 150through the connection line 152 enter the scanning unit 141 in the formof a parallel light flux. Moreover, the lens 142 acts so as to convergethe fundus oculi reflection light of the signal light LS passed throughthe scanning unit 141.

FIG. 2 shows one example of a specific configuration of the scanningunit 141. The scanning unit 141 comprises Galvano mirrors 141A and 141B,and reflection mirrors 141C and 141D.

The Galvano mirrors 141A and 141B are rotatable about rotary shafts 141a and 141 b, respectively. The rotary shafts 141 a and 141 b aredisposed so as to orthogonal to each other.

In FIG. 2, the rotary shaft 141 a of the Galvano mirror 141A is disposedin a direction parallel to the sheet of FIG. 2, and the rotary shat 141b of the Galvano mirror 141B is disposed in a direction parallel to thesheet of FIG. 2, and the rotary shaft 141 b disposed to a directionorthogonal to the sheet of FIG. 2. That is to say, the Galvano mirror141B is formed so as to be rotatable in the directions indicated by anarrow pointing in both directions in FIG. 2, whereas the Galvano mirror141A is formed so as to be rotatable in the directions orthogonal to thearrow pointing in both the directions. Consequently, the pair of Galvanomirrors 141A and 141B act so as to change the reflecting directions ofthe signal light LS to directions orthogonal to each other.

Here, a rotation movement of each of the Galvano mirrors 141A and 141Bis driven by a drive mechanism (mirror drive mechanisms 241 and 242shown in FIG. 5 including driving devices such as a motor. The signallights LS reflected by the Galvano mirrors 141A and 141B are reflectedby reflection mirrors 141C and 141D, thereby traveling in the samedirection as having entered into the Galvano mirror 141A.

As described before, the conductive optical fiber 152 a runs the opticalfiber 152 a is arranged facing the lens 142. The signal light LS emittedfrom this end face 152 b travels while expanding its beam diametertoward the lens 142. The light is converged into a parallel light fluxby this lens 142. On the contrary, the signal light LS passed throughthe fundus oculi Ef is converged toward the end face 152 b by the lens142.

[Configuration of OCT Unit]

Next, the configuration of the OCT unit 150 will be described referringto FIG. 3. The OCT unit 150 shown in FIG. 3 has almost the same opticalsystem as the conventional optical image measurement device. The OCTunit 150 comprises an interferometer that splits light emitted from thelight source into a reference light and a signal light, and generatesinterference light by superposing the reference light passed through areference object and the signal light passed through a measurementobject (fundus oculi Ef). The result of detection of the interferencelight is analyzed, whereby a tomographic image or 3-dimensional image ofthe fundus oculi Ef is formed.

A low coherence light source 160 is composed of a broadband lightsource, such as a super luminescent diode (SLD) and a light emittingdiode (LED), configured to emit a low coherence light L0. This lowcoherence light L0 is, for example, a light that has a wavelength of thenear-infrared region and has a temporal coherence length ofapproximately several tens of micrometers. The low coherence light L0has a longer wavelength than the illumination light (wavelength: about400 nm through 800 nm) of the retinal camera unit 1A, for example, awavelength of about 800 nm through 900 nm.

The low coherence light L0 emitted from the low coherence light source160 is guided to an optical coupler 162 through an optical fiber 161composed of, for example, a single mode fiber or a PM (Polarizationmaintaining) fiber. The optical coupler 162 splits this low coherencelight L0 into a reference light LR and the signal light LS.

Although the optical coupler 162 acts as both a part for splitting light(i.e., splitter) and a part for superposing lights (i.e., coupler), theoptical coupler 162 will be herein referred to as an “optical coupler”idiomatically.

The reference light LR generated by the optical coupler 162 is guided byan optical fiber 163 composed of a single mode fiber or the like, andemitted from the end face of the fiber. The emitted reference light LRis converged into a parallel light flux by a collimator lens 171, passedthrough a glass block 172 and a density filter 173, and then reflectedby a reference mirror 174 (reference object).

The reference light LR reflected by the reference mirror 174 is againpassed through the density filter 173 and the glass block 172, andconverged to the fiber end face of the optical fiber 163 by thecollimator lens 171. The converged reference light LR is guided to theoptical coupler 162 through the optical fiber 163.

The glass block 172 and the density filter 173 act as a delaying partfor making the optical path lengths (optical distances) of the referencelight LR and the signal light LS coincide, and also as a part for makingthe dispersion characteristics of the reference light LR and the signallight LS coincide.

Further, the reference mirror 174 is configured to be movable along thetraveling direction (the direction of the arrow pointing both sidesshown in FIG. 3) of the reference light LR. Consequently, the opticalpath length of the reference light LR according to the axial length ofthe eye E, etc. is ensured. The reference mirror 174 is moved by a drivemechanism (a reference mirror driving mechanism 243 shown in FIG. 5;described later) including a driving part such as a motor.

On the other hand, the signal light LS generated by the optical coupler162 is guided to the end of the connection line 152 through an opticalfiber 164 composed of a single mode fiber or the like. The conductiveoptical fiber 152 a runs inside the connection line 152. Herein, theoptical fiber 164 and the optical fiber 152 a may be composed of asingle optical fiber, or may be jointly formed by connecting the endfaces of the respective fibers. In either case, it is sufficient as faras the optical fiber 164 and 152 a are configured to be capable oftransferring the signal light LS between the retinal camera unit 1A andthe OCT unit 150.

The signal light LS is led through the inside of the connection line 152and guided to the retinal camera unit 1A. Then, the signal light LSenters into the eye E through the lens 142, the scanning unit 141, thedichroic mirror 134, the imaging lens 126, the relay lens 125, thevariable magnifying lens 124, the imaging diaphragm 121, the aperture112 a of the aperture mirror 112, and the objective lens 113. (At thismoment, the barrier filters 122 and 123 are retracted from the opticalpath, respectively.)

The signal light LS having entered the eye E forms an image on thefundus oculi (retina) Ef and is then reflected. At this moment, thesignal light LS is not only reflected on the surface of the fundus oculiEf, but also scattered at the refractive index boundary after reachingthe deep area of the fundus oculi Ef. As a result, the signal light LSpassed through the fundus oculi Ef is a light containing informationreflecting the state of the surface of the fundus oculi Ef andinformation reflecting the state of backscatter at the refractive indexboundary of the deep area tissue of the fundus oculi Ef. This light maybe simply referred to as “fundus oculi reflection light of the signallight LS.”

The fundus oculi reflection light of the signal light LS travelsreversely on the above path to be converged at the end face 152 b of theoptical fiber 152 a, enters into the OCT unit 150 through the opticalfiber 152 a, and returns to the optical coupler 162 through the opticalfiber 164. The optical coupler 162 superimposes the signal light LS andthe reference light LR reflected by the reference mirror 174, therebygenerating the interference light LC. The generated interference lightLC is guided into a spectrometer 180 through an optical fiber 165composed of a single mode fiber or the like.

Although a Michelson-type interferometer is adopted in the presentembodiment, for instance, a Mach Zender type, etc. and any type ofinterferometer may be adopted appropriately.

The spectrometer 180 comprises a collimator lens 181, a diffractiongrating 182, an image-forming lens 183, and a CCD 184. The diffractiongrating 182 in the present embodiment is a transmission-type diffractiongrating that transmits light; however, needless to say, areflection-type diffraction grating that reflects light may also beused. Moreover, needless to say, it is also possible to adopt, in placeof the CCD 184, other photo-detecting elements.

The interference light LC having entered the spectrometer 180 is split(resolved into spectra) by the diffraction grating 182 after convergedinto a parallel light flux by the collimator lens 181. The splitinterference light LC forms an image on the image pick-up surface of theCCD 184 by the image-forming lens 183. The CCD 184 receives theinterference light LC and converts to electrical detection signals, andoutputs the detection signals to the arithmetic and control unit 200.

[Configuration of Arithmetic and Control Unit]

Next, the configuration of the arithmetic and control unit 200 will bedescribed. This arithmetic and control unit 200 performs a process ofanalyzing the detection signals inputted from the CCD 184 of thespectrometer 180 of the OCT unit 150, and forming tomographic images ofthe fundus oculi Ef of the eye E. A technique for this analysis is thesame as a conventional technique for the Fourier domain OCT.

Further, the arithmetic and control unit 200 performs a process offorming (image data of) a 2-dimensional image showing the state of thesurface (retina) of the fundus oculi Ef, based on the video signalsoutputted from the imaging devices 10 and 12 of the retinal camera unit1A.

Furthermore, the arithmetic and control unit 200 executes control ofeach part of the retinal camera unit 1A and the OCT unit 150.

Control of the retinal camera unit 1A is, for example: control ofemission of illumination light by the observation light source 101 orthe imaging light source 103; control of insertion/retraction operationsof the exciter filters 105 and 106 or the barrier filters 122 and 123to/from the optical path; control of the operation of a display devicesuch as the LCD 140; control of shift of the illumination diaphragm 110(control of the diaphragm value); control of the diaphragm value of theimaging diaphragm 121; and control of shift of the variable magnifyinglens 124 (control of the magnification). Moreover, the arithmetic andcontrol unit 200 executes control of the rotation operation of theGalvano mirrors 141A and 141B inside the scanning unit 141.

On the other hand, control of the OCT unit 150 is, for example: controlof emission of the low coherence light L0 by the low coherence lightsource 160; control of shift of the reference mirror 174; and control ofthe accumulated time of the CCD 184.

One example of the hardware configuration of the arithmetic and controlunit 200 that acts as described above will be described referring toFIG. 4. The arithmetic and control unit 200 has the same hardwareconfiguration as that of a conventional computer. To be specific, thearithmetic and control unit 200 comprises: a microprocessor 201 (CPU,MPU, etc.), a RAM202, a ROM203, a hard disk drive (HDD) 204, a keyboard205, a mouse 206, a display 207, an image forming board 208, and acommunication interface (I/F) 209. These parts are connected via a bus200 a.

The microprocessor 201 executes operations characteristic to the presentembodiment, by loading a control program 204 a stored in the hard diskdrive 204, onto the RAM 202.

Further, the microprocessor 201 executes control of each part of thedevice described above, various arithmetic processes, etc. Moreover, themicroprocessor 201 executes control of each part of the devicecorresponding to an operation signal from the keyboard 205 or the mouse206, control of a display process by the display 207, and control of atransmission/reception process of various data, control signals and soon by the communication interface 209.

Various kinds of information, including patient information such as apatient name and a patient ID and image data of a fundus oculi image,are stored in the hard disk drive 204. As the patient information,information (reference mirror position information) indicating theposition of the reference mirror 174 during image measurement of afundus oculi conducted by the OCT unit 150, and information (scanposition information) indicating the scan positions such as scan startposition, scan end position, or scan intervals of signal lights.

The keyboard 205, the mouse 206 and the display 207 are used as userinterfaces in the fundus oculi observation device 1. The keyboard 205 isused as, for example, a device for typing letters, figures, etc. Themouse 206 is used as a device for performing various input operations tothe display screen of the display 207.

Further, the display 207 is any display device composed of an LCD, a CRT(Cathode Ray Tube) display or the like. The display 207 displays variousimages of the fundus oculi Ef formed by the fundus oculi observationdevice 1, and displays various screens such as an operation screen and aset-up screen.

The user interface of the fundus oculi observation device 1 is notlimited to the above configuration, and may be configured by using anyuser interface having a function of displaying and outputting variousinformation, and a function of inputting various information andoperating the device, such as a track ball, a control lever, a touchpanel type of LCD, and a control panel for opthalmology examinations.

The image forming board 208 is a dedicated electronic circuit for aprocess of forming (image data of) images of the fundus oculi Ef of theeye E. This image forming board 208 is provided with a fundus oculiimage forming board 208 a and an OCT image forming board 208 b. Thefundus oculi image forming board 208 a is a dedicated electronic circuitthat operates to form image data of fundus oculi images based on thevideo signals from the imaging device 10 and the imaging device 12 ofthe retinal camera unit 1A. Further, the OCT image forming board 208 bis a dedicated electronic circuit that operates to form image data offundus oculi images (tomographic images) of the fundus oculi Ef, basedon the detection signals from the CCD 184 of the spectrometer 180 in theOCT unit 150. By providing the image forming board 208, it is possibleto increase the processing speed for forming image data of fundus oculiimages and tomographic images.

The communication interface 209 performs a process of sending controlsignals from the microprocessor 201, to the retinal camera unit 1A orthe OCT unit 150. Moreover, the communication interface 209 performs aprocess of receiving video signals from the imaging devices 10 and 12 ofthe retinal camera unit 1A and detection signals from the CCD 184 of theOCT unit 150, and inputting the signals to the image forming board 208.At this time, the communication interface 209 operates to input thevideo signals from the imaging devices 10 and 12, to the fundus oculiimage forming board 208 a, and input the detection signal from the CCD184, to the OCT image forming board 208 b.

Further, in a case where the arithmetic and control unit 200 isconnected to a network such as a LAN (Local Area Network) and theInternet, it is possible to configure so as to be capable of datacommunication via the network, by providing the communication interface209 with a network adapter like a LAN card or communication equipmentlike a modem. In this case, it is possible to mount a serveraccommodating the control program 204 a, and also configure thearithmetic and control unit 200 as a client terminal of the server.

Furthermore, it is possible to configure so as to store any of thevarious kinds of information (described before) stored in the hard diskdrive 204, into a server on a network or into a database.

[Configuration of Control System]

The configuration of the control system of the fundus oculi observationdevice 1 having the aforementioned configuration will be describedreferring to FIG. 5. FIG. 5 shows a part relating to the operation andprocess relating to the present invention particularly selected fromamong the components of the fundus oculi observation device 1.

The control system of the fundus oculi observation device 1 isconfigured mainly having a controller 210 of the arithmetic and controlunit 200. The controller 210 comprises the microprocessor 201, theRAM202, the ROM203, the hard disk drive 204 (control program 204 a), andthe communication interface 209.

The controller 210 executes the aforementioned controlling processesthrough the microprocessor 201 operating based on the control program204 a. In specific, the controller 210 controls the mirror drivemechanisms 241 and 242 of the retinal camera unit 1A, respectively,thereby causing the Galvano mirrors 141A and 141B to operateindependently.

Further, the controller 210 executes control for causing the display 207of the user interface 240 to display two types of images captured by thefundus oculi observation device 1: that is, a 2-dimensional image(fundus oculi image Ef′) of the surface of the fundus oculi Ef obtainedby the retinal camera unit 1A, and an image of the fundus oculi Efformed based on the detection signals obtained by the OCT unit 150.These images may be displayed on the display 207 separately, or may bedisplayed side by side simultaneously.

An image forming part 220 performs a process of forming a fundus oculiimage based on video signals from the imaging devices 10 and 12 of theretinal camera unit 1A, and a process of forming a fundus oculi imagebased on detection signals from the CCD 184 of the OCT unit 150. Theimaging forming part 220 comprises the imaging forming board 208.

The image processor 230 applies various image processing to a fundusoculi image formed by the image forming part 220. For example, the imageprocessor 230 executes a process of forming a 3-dimensional image of thefundus oculi Ef based on the tomographic images of the fundus oculi Ef′based on the detection signals from the OCT unit 150, and variouscorrection processes such as brightness correction and dispersioncorrection of the images.

Further, the image processor 230 executes a characteristic process inthe present invention (described later): forms one tomographic image bycalculating based on tomographic images of two or more cross sections.The image processor 230 is to function as one example of the imageprocessor of the present invention.

The user interface (UI) 240 is equipped with input devices (operationdevices) such as a keyboard 205 and a mouse 206, and a display devicesuch as a display 207.

The image storage 250 stores the (image data of) images formed by theimage forming part 220 or the image processor 230. The image storage 250includes a storage device such as a hard disk drive 204. The arithmeticand control device 200 is equivalent to one example of the imageprocessing device of the present invention, and the image storage 250functions as one example of the storage of the present invention.

Herein, a mode of control of scan of the signal light LS by thecontroller 210, and a mode of a process to a detection signal from theOCT unit 150 by the image forming part 220 and the image processor 230will be respectively described. An explanation regarding the process bythe image forming part 220, etc., to the video signal from the retinalcamera unit 1A will be omitted because it is the same as theconventional process.

[Signal Light Scanning]

Scan of the signal light LS is performed by changing the directions ofthe reflecting surfaces of the Galvano mirrors 141A and 141B of thescanning unit 141 in the retinal camera unit 1A. By controlling themirror drive mechanisms 241 and 242 respectively to change thedirections of the reflecting surfaces of the Galvano mirrors 141A and141B respectively, the controller 210 scans the application position ofthe signal light LS on the fundus oculi Ef.

When the facing direction of the reflecting surface of the Galvanomirror 141A is changed, the signal light LS is scanned in the horizontaldirection (x-direction in FIG. 1) on the fundus oculi Ef. On the otherhand, when the facing direction of the reflecting surface of the Galvanomirror 141B is changed, the signal light LS is scanned in the verticaldirection (y-direction in FIG. 1) on the fundus oculi Ef. Further, bychanging the facing directions of the reflecting surfaces of both theGalvano mirrors 141A and 141B simultaneously, it is possible to scan thesignal light LS in the composed direction of the x-direction andy-direction. That is, by controlling these two Galvano mirrors 141A and141B, it is possible to scan the signal light LS in any direction on thex-y plane.

FIGS. 6A and 6B show an example of a mode of scan of the signal light LSfor forming an image of the fundus oculi Ef. FIG. 6A shows an example ofa mode of scan of the signal light LS, when the fundus oculi Ef is seenfrom a direction that the signal light LS enters the eye E (that is,seen from −z side toward +z side in FIG. 1). Further, FIG. 6B shows oneexample of the feature of arrangement of scanning points (positions atwhich image measurement is carried out) on each scanning line on thefundus oculi Ef.

As shown in FIG. 6A, the signal light LS is scanned within arectangular-shaped scanning region R that has been preset. Within thisscanning region R, a plurality of (m number of) scanning lines R1through Rm are set in the x-direction. When the signal light LS isscanned along the respective scanning lines Ri (i=1 through m),detection signals of the interference light LC are generated.

Herein, a direction of each scanning line Ri will be referred to as the“main scanning direction” and a direction orthogonal thereto will bereferred to as the “sub-scanning direction”. Accordingly, scanning ofthe signal light LS in the main scanning direction is performed bychanging the facing direction of the reflecting surface of the Galvanomirror 141A, and scanning in the sub-scanning direction is performed bychanging the facing direction of the reflecting surface of the Galvanomirror 141B.

On each scanning line Ri, as shown in FIG. 6B, a plurality of (n numberof) scanning points Ri1 through Rin are preset.

In order to execute the scanning shown in FIGS. 6A and 6B, thecontroller 210 firstly controls the Galvano mirrors 141A and 141B to setthe target of the signal light LS entering into the fundus oculi Ef to ascan start position RS (scanning point R11) on the first scanning lineR1. Subsequently, the controller 210 controls the low coherence lightsource 160 to flush the low coherence light L0, thereby making thesignal light LS enter the scan start position RS. The CCD 184 receivesthe interference light LC based on the fundus oculi reflection light ofthis signal light LS at the scan start position RS, and outputs thedetection signal to the controller 210.

Next, the controller 210 controls the Galvano mirror 141A to scan thesignal light LS in the main scanning direction and set the incidenttarget of the signal light LS to a scanning point R12, and makes the lowcoherence light L0 flushed to make the signal light LS enter into thescanning point R12. The CCD 184 receives the interference light LC basedon the fundus oculi reflection light of this signal light LS at thescanning point R12, and then outputs the detection signal to thecontroller 210.

Likewise, the controller 210 obtains detection signals outputted fromthe CCD 184 in response to the interference light LC for each scanningpoint, by flushing the low coherence light L0 at each scanning pointwhile shifting the incident target of the signal light LS from scanningpoint R13 to R14, - - - , R1 (n−1), and R1 n in order.

When the measurement at the last scanning point R1 n of the firstscanning line R1 is finished, the controller 210 controls the Galvanomirrors 141A and 141B simultaneously to shift the incident target of thesignal light LS to the first scanning point R21 of the second scanningline R2 following a line switching scan r. Then, by conducting thepreviously described measurement on each scanning point R2 j (j=1through n) of this second scanning line R2, detection signalscorresponding to the respective scanning points R2 j are obtained.

Likewise, the measurement is conducted for each of the third scanningline R3, - - - , the m−1th scanning line R(m−1), the mth scanning lineRm to obtain the detection signals corresponding to the respectivescanning points. Symbol RE on a scanning line Rm is a scan end positioncorresponding to a scanning point Rmn.

As a result, the controller 210 obtains m×n number of detection signalscorresponding to m×n number of scanning points Rij (i=1 through m, j=1through n) within the scanning region R. Hereinafter, a detection signalcorresponding to the scanning point Rij may be represented by Dij.

Such interlocking control of the shift of scanning points and theemission of the low coherence light L0 can be realized by synchronizing,for instance, timing for transmission of control signals to the mirrordrive mechanisms 241 and 242 and timing for transmission of controlsignals (output request signals) to the low coherence light source 160.

As described above, when each of the Galvano mirrors 141A and 141 B isoperated, the controller 210 stores the position of each scanning lineRi and the position of each scanning point Rij (coordinates on the x-ycoordinate system) as information representing the content of theoperation. This stored content (scan position information) is used in animage forming process as in conventional one.

[Image Processing]

Next, an example of a process on OCT images (tomography images of thefundus oculi Ef) by the image forming part 220 and the image processor230 will be described.

The image forming part 220 executes the formation process of tomographicimages of the fundus oculi Ef along each scanning line Ri (main scanningdirection). Further, the image processor 230 executes the formationprocess of a 3-dimensional image of the fundus oculi Ef based on thesetomographic images formed by the image forming part 220, etc.

The formation process of a tomographic image by the image forming part220, as in the conventionally one, includes a 2-step arithmetic process.In the first step of the arithmetic process, based on a detection signalDij corresponding to each scanning point Rij, an image in the depth-wisedirection (z-direction in FIG. 1) of the fundus oculi Ef at the scanningpoint Rij is formed.

FIG. 7 shows a mode of a tomographic image formed by the image formingpart 220. In the second step of the arithmetic process, on each scanningline Ri, based on the images in the depth-wise direction at the n numberof scanning points Ri1 through Rin, a tomographic image G1 of the fundusoculi Ef along the scanning line Ri is formed. Then, the image formingpart 220 determines the arrangement and the distance of the scanningpoints Ri1 through Rin referring to the positional information (scanposition information described before) of the scanning points Ri1through Rin, and forms a tomographic image Gi along this scanning lineRi. Through the above process, m number of tomographic images (a groupof tomographic images) G1 through Gm at different positions in thesub-scanning direction (y-direction) are obtained.

Here, the formation process of a 3-dimensional image of the fundus oculiEf by the image processor 230 will be explained. A 3-dimensional imageof the fundus oculi Ef is formed based on the m number of tomographicimages obtained through the above arithmetic process. The imageprocessor 230 forms a 3-dimensional image of the fundus oculi Ef byperforming a known interpolating process to interpolate an image betweenthe adjacent tomographic images Gi and G (i+1).

Here, the image processor 230 determines the arrangement and thedistance of each scanning line Ri while referring to the positionalinformation of each scanning line Ri to form this 3-dimensional image.For this 3-dimensional image, a 3-dimensional coordinate system (x, y,z) is set, based on the positional information (the scan positioninformation) of each scanning point Rij and the z-coordinate in thedepth-wise image.

Furthermore, based on this 3-dimensional image, the image processor 230can form a tomographic image of the fundus oculi Ef at a cross-sectionin any direction other than the main scanning direction (x-direction).Once the cross-section is designated, the image processor 230 determinesthe position of each scanning point (and/or an interpolated depth-wiseimage) on this designated cross-section, and extracts a depth-wise imageat each determined position (and/or an interpolated depth-wise image),thereby forming a tomographic image of the fundus oculi Ef at thedesignated cross-section by arranging plural extracted depth-wiseimages.

Furthermore, an image Gmj shown in FIG. 7 represents an image in thedepth-wise direction (z-direction) at the scanning point Rmj on thescanning line Rm. A depth-wise image at each scanning point Rij on thescanning line Ri formed by the first-step arithmetic process isrepresented as “image Gij.”

[Operation]

An operation of the fundus oculi observation device 1 having theaforementioned configuration will be described. A flowchart shown inFIG. 8 represents an example of the operation of the fundus oculiobservation device 1. First, the fundus oculi observation device 1captures a 2-dimensional image (fundus oculi image Ef′) of the surfaceof the fundus oculi Ef of the eye E (S1), and obtains tomographic imagesGi (i=1 to m) of the fundus oculi Ef (S2).

The controller 210 causes the image storage 250 to store (the image dataof) the fundus oculi image Ef′ and (the image data of) the tomographicimages Gi. In the case of executing only the process relating to thepresent invention, it is not necessary to capture the fundus oculi imageEf′ in Step S1.

The controller 210 reads out the tomographic images G1 to Gm from theimage storage 250, and sends the images to the image processor 230. Eachof the tomographic images Gi is a tomographic image having a crosssection extending in the depth-wise direction (+z direction) of thefundus oculi Ef from a scanning line Ri. The cross section of thetomographic image Gi may be referred as the “cross section correspondingto the scanning line Ri” hereinafter.

The image processor 230 executes an arithmetic operation based on thetomographic image Gi (i=2 to m−1), tomographic images G (i+1) andtomographic images G (i−1), thereby forming a new tomographic image atthe cross section corresponding to the scanning line Ri (S3 to S5).Below, this process will be described in detail.

The tomographic image Gi has the cross section corresponding to thescanning line Ri. The tomographic images G (i+1) and G (i−1)respectively have a cross section corresponding to a scanning line R(i+1) and a cross section corresponding to a scanning line R (i−1),which are adjacent to the scanning line Ri. Therefore, the cross sectioncorresponding to the scanning line R (i+1) and the cross sectioncorresponding to the scanning line R (i−1) are adjacent to the crosssection corresponding to the scanning line Ri, respectively. Moreover,the cross sections corresponding to the scanning lines Ri, R (i+1) and R(i−1) are arranged in the y direction as shown in FIG. 9.

In relation to the aforementioned new tomographic image, an example ofthe process for determining the pixel value of a pixel at an optionalposition Pi=(xi, yi, zi) in the cross section corresponding to thescanning line Ri will be described. By thus determining the pixel valueof the pixel at the arbitrary position Pi, it is possible to form theaforementioned new tomographic image.

First, the image processor 230 obtains the coordinate values of pixelsof the tomographic images G (i+1) and G (i−1) corresponding to theposition Pi (S3).

For this purpose, the image processor 230 obtains the equation of astraight line that is through the position Pi and parallel to the ydirection (a dotted part in FIG. 9), and further obtains the coordinatesof the position P (i+1) where the straight line intersects with thetomographic image G (i+1). The coordinates of the position P (i+1) are(xi, y (i+1), zi), which are the coordinate values of the pixel of thetomographic image P (i+1) corresponding to the position Pi. Likewise,the coordinate values of the position P (i−1) where the straight lineintersects with the tomographic image G (i−1) are (xi, y (i−1), zi),which are coordinate values of the tomographic image P (i−1)corresponding to the position Pi.

Here, yi, y (i+1) and y (i−1) are y coordinate values of the scanninglines Ri, R (i+1) and R (i−1), respectively, shown in FIG. 6A. Further,the y coordinate values of the respective scanning lines Ri, R (i+1) andR (i−1) can be acquired from the aforementioned scan positioninformation. Therefore, instead of using a straight line as describedabove, it is possible to use the y coordinate values y(i+1) and y(i−1)of the scanning lines R(i+1) and R(i−1), thereby obtaining thecoordinate values (xi, y(i+1), zi), (xi, y(i−1), zi) of the pixels ofthe tomographic images G(i+1) and G(i−1) corresponding to the positionPi.

Next, the image processor 230 calculates the average value of the pixelvalue of the pixel at the position Pi of the tomographic image Gi, thepixel value of the pixel at the position P(i+1) of the tomographic imageG(i+1) and the pixel value of the pixel at the position P(i−1) of thetomographic image G(i−1) (S4).

Here, it is possible to properly use any arithmetic method for obtainingone value by executing a statistical calculation for a plurality ofvalues (may be referred as “average value etc.”), such as the median,instead of the average value of these pixel values.

After calculating the aforementioned average value etc. for each of thepositions Pi, the image processor 230 arranges a pixel having theaverage value etc. as a pixel value, at each of the positions Pi,thereby forming a tomographic image (S5). This tomographic image is atargeted tomographic image, that is, a new tomographic image at thecross section corresponding to the scanning line Ri.

The image processor 230 executes the process of Steps S3 to S5 for eachof the tomographic images Gi(i=2 to m−1).

Furthermore, the image processor 230 executes the similar process asdescribed above by using tomographic images G1 and G2 to thereby form anew tomographic image at a cross section corresponding to a scanningline R1 (S6), and executes the similar process as described above byusing tomographic images Gm and G(m−1) to thereby form a new tomographicimage at a cross section corresponding to a scanning line Rm (S7).

The controller 210 causes the image storage 250 to store m number of newtomographic images that have been formed in Steps S5 to S7. Further, theimage processor 230 can form a 3-dimensional image of the fundus oculiEf based on the new tomographic images that have been formed in Steps S5to S7 if necessary. Moreover, the image processor 230 can form atomographic image at any cross section of the fundus oculi Ef ifnecessary, based on the 3-dimensional image. This is the end of theexplanation for the operation of the fundus oculi observation device 1relating to the present embodiment.

[Actions and Advantageous Effects]

The actions and advantageous effects of the fundus oculi observationdevice 1 (optical image measurement device) relating to the presentembodiment that operates as described above will be explained.

This fundus oculi observation device 1 acts so as to, for a crosssection corresponding to each scanning line Ri, execute an arithmeticoperation based on a tomographic image Gi at this cross section, atomographic image G(i+1) at a cross section corresponding to a scanningline R(i+1) and a tomographic image G(i−1) at a cross sectioncorresponding to a scanning line R(i−1), thereby forming a newtomographic image at the cross section corresponding to the scanningline Ri.

This new tomographic image is formed by using the result of measurementat a single cross section (the cross section corresponding to thescanning line Ri) and the result of measurement at other cross sections(the cross sections corresponding to the scanning lines R(i+1) andR(i−1)).

Therefore, according to the fundus oculi observation device 1, it ispossible to increase the image quality of a tomographic image to beformed, compared with the conventional configuration of forming atomographic image based on only the result of measurement at a singlecross section. Further, by forming a 3-dimensional image based on thesenew tomographic images, it is possible to acquire a 3-dimensional imagewith higher image quality than conventional. Moreover, by forming atomographic image at an arbitrary cross section based on this3-dimensional image, it is possible to acquire a tomographic image withhigher image quality than conventional.

Further, the fundus oculi observation device 1 is configured to, in theprocess for forming a new tomographic image at a cross sectioncorresponding to a scanning line Ri, refer to tomographic images atcross sections corresponding to scanning lines R(i+1) and R(i−1), whichare adjacent to the cross section corresponding to the scanning line Ri,so that it is possible to increase the image quality of a newtomographic image to be formed.

Moreover, the fundus oculi observation device 1 is configured tocalculate the average value etc. of the pixel value of the pixel of thetomographic image Gi at a position Pi and the pixel values of the pixelsof the tomographic images G(i+1) and G(i−1) at positions P(i+1) andP(i−1) corresponding to the position Pi, and form a new tomographicimage having the average value etc. as the pixel value of the pixels atthe position Pi. By executing such a statistical calculation to obtainthe pixel value of each pixel and form a new tomographic image, it ispossible to increase the image quality.

[Modification]

The configuration described in detail above is merely an example forfavorably implementing the optical image measurement device relating tothe present invention. Therefore, it is possible to properly apply anymodification within the scope of the present invention. Below, varioustypes of modifications of the optical image measurement device accordingto the present invention will be described.

In the above embodiment, a new tomographic image is formed for a crosssection of each tomographic image Gi (i=1 to m) acquired in Step S2.However, it is also possible to form new tomographic images for only anarbitrary number of cross sections among the cross sections of thetomographic image Gi.

In the above embodiment, for a cross section of each tomographic imageGi (i=2 to m−1), a new tomographic image is formed with tomographicimages G(i+1) and G(i−1) located on both sides of the tomographic imageGi. However, it is also possible to form a new tomographic image withtomographic images G(i+1) . . . G(i+p), G(i−1) . . . G(i−q) at anarbitrary number of cross sections that are adjacent to the crosssection of the tomographic image Gi (herein, p≧0, q≧0, 1≦p+q≦m−1).

“To be adjacent to a cross section of a tomographic image Gi” means “tobe included in the range of a distance from the cross section or of thenumber of cross sections, which is previously set as tomographic imagesof other cross sections used in the process of forming a new tomographicimage at the cross section.

In a case where the range of the distance (for example, 0<dist≦D) ispreviously set and an interval of adjacent cross sections is d, theimage processor 230 forms a new tomographic image at the cross sectionby involving tomographic images of [D÷d] number on both sides (or oneside) of the cross section (herein, [·] is the Gauss symbol).

Further, in a case where the range of the number of cross sections M≧1is previously set, the image processor 230 forms a new tomographic imageat the cross section by involving M number of tomographic images on bothsides (or one side) of the cross section.

Moreover, also for each of the cross sections of the tomographic imagesG1 and Gm, it is possible to form a new tomographic image by involvingtomographic images at any number of cross sections adjacent to the crosssection.

In the embodiment described before, tomographic images at a plurality ofcross sections arranged so as to be parallel to each other have beendescribed. However, the pattern of the cross sections is optional.

For example, as shown in FIG. 10, there is a case of acquiringtomographic images H1 to H6 at a plurality of (six) cross sectionsarranged concentrically. The process of forming a new tomographic imageat a cross section of a tomographic image H4 in this case will bedescribed. Here, symbol C represents a center position (referred to as ascan center) of circular scan of a signal light LS for acquiring thetomographic images H1 to H6 at the cross sections arrangedconcentrically. The number of cross sections arranged concentrically isgenerally numerous (several dozens to several hundreds).

First, for an arbitrary position Q4 of the cross section of thetomographic image H4, the image processor 230 obtains the equation of astraight line connecting the position Q4 and the scan center C (a dottedline part in FIG. 10). Next, the image processor 230 obtains positionsQ3 and Q5 where the straight line crosses the cross sections oftomographic images H3 and H5, respectively. The positions Q3 and Q5 arepositions of the cross sections of the tomographic images H3 and H5corresponding to the position Q4 of the cross section of the tomographicimage H4. Furthermore, the image processor 230 calculates an averagevalue etc. of the pixel value of a pixel of the position Q4, the pixelvalue of a pixel of the position Q3 and the pixel value of a pixel a ofthe position Q5. By executing this process for each position Q4 of thecross section of the tomographic image H4, it is possible to form a newtomographic image at the cross section.

Next, acquisition of a tomographic image at a spirally-shaped crosssection will be described. Although the spirally-shaped cross section isa single cross section, a cross section for one rotation around a spiralcenter is here defined as one cross section. Thus, it is possible toform a new tomographic image at any position of the spirally-shapedcross section, in the same manner as in the case of the cross sectionsarranged concentrically.

Next, acquisition of tomographic images at a plurality ofradially-arranged cross sections will be described. FIG. 11 showstomographic images J1 to J4 of four cross sections arranged radially.Herein, symbol S represents the intersection of these cross sections.The number of radially-arranged cross sections is generally numerous(several dozens to several hundreds).

First, for an optional position U3 of the cross section of a tomographicimage J3, the image processor 230 obtains the equation of a circle thattakes the cross-section intersection S as the center thereof and passesthrough the position U3 (a dotted line part in FIG. 11). Next, the imageprocessor 230 obtains positions U2 and U4 where this circle crosses thecross sections of the tomographic images J2 and J4, respectively. Thepositions U2 and U4 are positions in the cross sections of thetomographic images J2 and J4 that correspond to the position U3 in thecross section of the tomographic image J3. Furthermore, the imageprocessor 230 calculates an average value etc. of the pixel value of apixel of the position U3, the pixel value of a pixel of the position U2and the pixel value of a pixel of the position U4. By executing thisprocess for each position U3 in the cross section of the tomographicimage J3, it is possible to form a new tomographic image at the crosssection.

It is possible to apply this process to any pattern of cross sections inwhich the cross sections cross each other, other than theradially-arranged cross sections.

In the above embodiment, the process of forming a fundus oculi image isexecuted by the image forming part 220 (image forming board 208), andvarious types of control process are executed by the controller 210(microprocessor 201 or the like). However, it is possible to configureso as to execute both the processes by using one or more computer(s).

In the above embodiment, a fundus oculi observation device having afunction of a retinal camera and a function of an optical imagemeasurement device has been described. However, it is also possible toapply the configuration of the present invention to a device havingother fundus oculi observation functions such as a function of a slitlamp (slit lamp microscopic device) and a function of an optical imagemeasurement device.

Further, the configuration according to the present invention isapplicable to not only the complex devices described above but also anormal optical image measurement device.

For example, it is possible to apply the configuration according to thepresent invention that automatically sets the position of a referenceobject, to any optical image measurement device configured to determinethe depth-wise position in a funds oculi based on the position of areference object, such as the optical image measurement device disclosedin Japanese Unexamined Patent Application Publication JP-A 2005-241464by the present inventors.

Further, it is possible to apply the configuration according to thepresent invention that automatically sets a scan position of a signallight, to any optical image measurement device having a configurationthat scans with a signal light by using a Galvano mirror or the like,such as the optical image measurement device disclosed in JapaneseUnexamined Patent Application Publication JP-A No. 2007-130403 by thepresent inventors.

Moreover, in the above embodiment, tomographic images of a fundus oculiare formed. However, the “measurement object” in the present inventionmay be any object from which tomographic images can be acquired by anoptical image measurement device, such as any living organs andindustrial products.

For execution of the process relating to the present invention with highaccuracy, the accuracy in positional relationship between onetomographic image to become a correction subject and another tomographicimage to be referred in the correction process is important (ref. FIG.9). Below, an example of this position-matching process will bedescribed.

As a first example, a method using an “accumulated image” described inJapanese Unexamined Patent Application Publications JP-A 2007-130403,JP-A 2007-252692, JP-A 2007-325831, etc. will be described.

An accumulated image is an image generated by accumulating tomographicimages in the depth-wise direction. Here, “to accumulate in thedepth-wise direction” means an arithmetic process of summing up(projecting), in the depth-wise direction, luminance values (pixelvalues) at the respective depth positions of images Gij of therespective depth-wise directions included in tomographic images. Adotted image acquired by accumulating the images Gij of the respectivedepth-wise directions has a luminance value obtained by, in thedepth-wise direction, summing up the luminance values at the respectivez positions of the images Gij in the depth-wise direction.

The process of forming an accumulated image is executed by the imageprocessor 230. Specifically, the image processor 230 accumulates therespective m×n number of images Gij in the depth-wise direction, therebyforming an accumulated image composed of m×n number of dotted imagesthat are 2-dimensionally distributed in a scanning region R. Thisaccumulated image becomes an image representing the form of the surfaceof the fundus oculi Ef, as well as the fundus oculi image Ef′(2-dimensional image of the fundus oculi surface) in the scanning regionR.

The image processor 230 matches the positions of the fundus oculi imageEf′ and the accumulated image. This process can be realized byspecifying a blood vessel region within the fundus oculi image Ef′ and ablood vessel region within the accumulated image and executingposition-matching of the blood vessel regions, as in the above document,for example. Consequently, the positional relation (positional relationin the x-y direction) of m number of tomographic images G1 to Gm can becorrected with reference to the fundus oculi image Ef′.

For the tomographic images G1 to Gm in which the positional relation hasbeen thus corrected, the image processor 230 obtains the coordinatevalues of pixels P(i+1) and P(i−1) of tomographic images G(i+1) andG(i−1), which correspond to an arbitrary pixel (position) Pi of eachtomographic image Gi (ref. to Step 3 in FIG. 8), and further executesthe process of Steps 4 and after shown in FIG. 8.

According to this modification, it is possible to enhance the accuracyin positional relation in the x-y direction between one tomographicimage Gi to become a subject to be corrected and other tomographicimages G(i+1) and G(i−1) referred in the correction process, and itbecomes possible to execute the process related to the present inventionwith high accuracy.

Likewise, it is also possible to enhance the accuracy in positionalrelation in the depth-wise direction by correcting the positionalrelation in the depth-wise direction (z direction) of the tomographicimages G1 to Gm. Herein, the process of correcting the positionalrelation in the depth-wise direction can be conducted by, for example,adjusting the z position of a tomographic image Gi so as to match thedepth position of a layer that is represented by the tomographic imageGi. This concludes the explanation of the first example.

Next, a second example is described. In the second example, a method ofenhancing the accuracy in positional relation between one tomographicimage to be a correction subject and other tomographic images referredin the correction process, by detecting movements of an eye referring afundus oculi image Ef′.

The fundus oculi image Ef′ used in the present example is, for example,a moving image for fundus oculi observation acquired with infraredillumination light. It is preferable if the frame rate of the movingimage is synchronized with the scan by a signal light LS (e.g., theswitching timing of the frames of the moving image is synchronized withthe switching timing of the scanning line Ri). More specifically, it ispreferred to acquire one frame every time one tomographic image Gi isacquired (that is, every time each scanning line Ri is scanned). Thus,it is possible to associate one frame with each of the tomographicimages Gi. Such synchronizing processes are executed by the controller210.

The image processor 230 specifies a characteristic image region(characteristic region) from an image within each frame thus acquired.The characteristic region can include, for example, an image regioncorresponding to the peripheral part of an optic disk, an image regioncorresponding to the center position of an optic disk, an image regioncorresponding to a macula part, an image region corresponding to abranching position or an end part of a blood vessel, and so on. Theprocess of specifying these characteristic regions can be executed by,for example, employing any known image-processing technique such as athreshold process for pixel values and a pattern recognition process. Itis to be noted that the same characteristic region is specified for therespective frames.

Subsequently, the image processor 230 obtains the position of thespecified characteristic region within a frame for the respectiveframes. Furthermore, based on these positions, the image processor 230obtains time-series changes of the position of the characteristic regionin the moving image. Consequently, for example, a displacement of thecharacteristic region within each of the frames with respect to theposition (reference position) of the characteristic region in the firstframe (presumed to be corresponding to the first scanning line R1) canbe observed. The displacement is a displacement in the x-y direction.

Based on the displacement of the characteristic region within each ofthe frames, the image processor 230 corrects the position in the x-ydirection of a tomographic image Gi that has been associated with theframe. The correction process is conducted by changing the position ofthe tomographic image Gi so as to set off the displacement. Then, theimage processor 230 executes the process from Step 3 and after shown inFIG. 8.

According to the modification, after positional offsetting of thetomographic image Gi attributed to movements of the eye E duringscanning with a signal light LS is corrected, the accuracy in positionalrelation in the x-y direction between one tomographic image Gi to becomea correction subject and other tomographic images G(i+1) and G(i−1)referred in the correction process can be enhanced. Therefore, itbecomes possible to execute the process related to the present inventionwith high accuracy. Moreover, it is also possible to execute apositional correction in the depth-wise direction like the one that hasbeen described in the above first example, along with the process of thesecond example.

[Image Processing Device]

The image processing device related to the present invention is nowdescribed. In the above embodiment, the arithmetic and control device200 is used as the image processing device.

The image processing device according to the present inventioncomprises: a storage configured to store a tomographic image at each ofa plurality of cross sections of a measurement object; and an imageprocessor configured to execute an arithmetic operation based on atomographic image at one cross section and other tomographic images ateach of one or more cross sections other than the one cross section,thereby forming a new tomographic image at the one cross section. In thearithmetic and control device 200 of the above embodiment, the imagestorage 250 functions as a storage, and the image processor 230functions as an image processor.

According to the image processing device, it is possible to increase theimage quality of a tomographic image to be formed, compared with theconventional configuration of forming a tomographic image based on onlythe result of measurement at a single cross section. Further, by forminga 3-dimensional image based on these new tomographic images, it ispossible to acquire a 3-dimensional image with higher image quality thanconventional. Moreover, by forming a tomographic image at an arbitrarycross section based on this 3-dimensional image, it is possible toacquire a tomographic image with higher image quality than conventional.

[Program]

A program for controlling the device related to the present invention isnow described. In the above embodiment, the control program 204 acorresponds to the program.

The program causes a computer such as the arithmetic and control unit200 that comprises a storage storing a tomographic image at each of aplurality of cross sections of a measurement object, to execute anarithmetic operation based on a tomographic image at one cross sectionand other tomographic images at each of one or more cross sections otherthan the one cross section and thereby form a new tomographic image atthe one cross section.

According to the program, it is possible to increase the image qualityof a tomographic image to be formed, compared with the conventionalconfiguration of forming a tomographic image based on only the result ofmeasurement at a single cross section. Further, by forming a3-dimensional image based on these new tomographic images, it ispossible to acquire a 3-dimensional image with higher image quality thanconventional. Moreover, by forming a tomographic image at an optionalcross section based on this 3-dimensional image, it is possible toacquire a tomographic image with higher image quality than conventional.

It is possible to properly apply modification for implementing variouskinds of processes described in the above embodiment to the imageprocessing device and program described above.

1. An optical image measurement device configured to form a tomographicimage at each of a plurality of cross sections of a measurement object,the optical image measurement device comprising: an image processorconfigured to execute an arithmetic operation based on a tomographicimage at one cross section of the plurality of cross sections andanother tomographic image at each of one or more cross sections otherthan the one cross section, thereby forming a new tomographic image atthe one cross section.
 2. The optical image measurement device accordingto claim 1, wherein: the image processor executes the arithmeticoperation based on the tomographic image at the one cross section andthe other tomographic image at a cross section adjacent to the one crosssection, thereby forming the new tomographic image.
 3. The optical imagemeasurement device according to claim 1, wherein: the image processorexecutes the arithmetic operation based on a pixel value of a pixel ofthe tomographic image at a specific position in the one cross sectionand a pixel value of a pixel of the other tomographic image at aposition corresponding to the specific position, thereby obtaining apixel value of a pixel of the new tomographic image at the specificposition.
 4. The optical image measurement device according to claim 2,wherein: the image processor executes the arithmetic operation based ona pixel value of a pixel of the tomographic image at a specific positionin the one cross section and a pixel value of a pixel of the othertomographic image at a position corresponding to the specific position,thereby obtaining a pixel value of a pixel of the new tomographic imageat the specific position.
 5. The optical image measurement deviceaccording to claim 3, wherein: the image processor calculates an averagevalue of the pixel value of the pixel of the tomographic image at thespecific position and the pixel value of the pixel of the othertomographic image at the position corresponding to the specificposition, as the pixel value of the pixel of the new tomographic imageat the specific position.
 6. The optical image measurement deviceaccording to claim 4, wherein: the image processor calculates an averagevalue of the pixel value of the pixel of the tomographic image at thespecific position and the pixel value of the pixel of the othertomographic image at the position corresponding to the specificposition, as the pixel value of the pixel of the new tomographic imageat the specific position.
 7. The optical image measurement deviceaccording to claim 3, wherein: the image processor calculates a medianof the pixel value of the pixel of the tomographic image at the specificposition and the pixel value of the pixel of the other tomographic imageat the position corresponding to the specific position, as the pixelvalue of the pixel of the new tomographic image at the specificposition.
 8. The optical image measurement device according to claim 4,wherein: the image processor calculates a median of the pixel value ofthe pixel of the tomographic image at the specific position and thepixel value of the pixel of the other tomographic image at the positioncorresponding to the specific position, as the pixel value of the pixelof the new tomographic image at the specific position.
 9. An imageprocessing device comprising: a storage configured to store atomographic image at each of a plurality of cross sections of ameasurement object; and an image processor configured to execute anarithmetic operation based on a tomographic image at one cross sectionof the plurality of cross sections and another tomographic image at eachof one or more cross sections other than the one cross section, therebyforming a new tomographic image at the one cross section.